1. Field of the Invention
The present invention relates to a liquid jet recording head for jetting liquid to form flying droplets to make a record.
2. Description of the Prior Art
A liquid jet recorder makes a record by discharging liquid such as ink from a nozzle of a recording head. This type of recorder has been warranted attention in that the noise generated during recording is negligible, it attains high speed recording and the record can be made on a plain paper without special treatment.
Among others, liquid jet recording methods disclosed in Japanese Patent Application Laid-Open No. 51875/1979 and West Germany DOLS No. 2843064 are unique compared with other liquid jet recording methods because thermal energy is applied to the liquid to produce a motive force for discharging droplets.
In the disclosed recording method, the liquid acted by the thermal energy causes a change of state with a rapid increase of volume, liquid is discharged from an orifice at an end of a recording head by a force due to the change of state to form flying droplets and the droplets are deposited on a record medium to form a record.
The liquid jet recording method disclosed in the West Germany DOLS No. 2843064, is not only effectively applied to a drop-on demand recording method but also allows easy implementation of a full-line type, high density multi-orifice recording head and hence it enables rapid formation of a high resolution and high quality image.
The recording head used in the above recording method comprises a liquid discharge unit including an orifice for discharging liquid and a liquid flow path having a heating unit by which a thermal energy for discharging droplets is applied to the liquid, and an electro-thermal converter for generating the thermal energy.
In the prior art recorder having a liquid jet recording head, wiring of the recording head extends on a substrate to a flexible wiring cable connected to a drive circuit which produces an electrical signal to drive the electro-thermal converter of the recording head. The connecting pads of the flexible cable for applying the electrical signal to the recording head have been connected to the wiring pads of the recording head by press-contact method, wire bonding method, soldering or thermal press-contact method, and thereafter the flexible cable is fixed to the recording head.
The substrate of the liquid jet recording head has one of different wiring and heat generating resistor patterns depending on an end product such as eight lines with 2.5 lines/mm for a desk top calculator printer or sixteen lines with 4 lines/mm for a facsimile machine.
FIG. 1 shows a structure of a prior art liquid jet recording head. Numeral 1 denotes a substrate, numeral 2 denotes electrodes through which electrical signals are supplied, numeral 3 denotes heat generating resistors which are electrothermal converters, numeral 4 denotes an area of a protection film which protects the electrodes and the heat generating resistors from liquid, and numeral 5 denotes a flexible cable for connecting the substrate to a drive circuit.
In the prior art liquid jet recording head, the wiring area 6 is large and hence the amount of the substrate material required for each head is large. Since the substrate is made of an expensive material such as Si, the increase of the cost of the recording head by the substrate is not negligible.
The increase of the size of the substrate by the unnecessary area causes the reduction of throughput in etching, sputtering or vapor deposition process and impedes mass-production.
Further, because the mask changes from product to product, the etching, sputtering or vapor deposition process is complex and yield is lowered due to misoperation.
Even in the unnecessary area, short-circuits and bridging of the wiring occur at the same probability as that in the necessary area. Thus, the unnecessary area causes the reduction of the yield.